One particularly advantageous application of the invention relates to the manufacture of lining elements, such as blades, of a sectored-type curing or vulcanizing mould for vehicle tires.
This type of mould mainly comprises two shells that each mould one of the lateral sidewalls of the tire, a plurality of sectors that mould the tread of said tire and are radially movable between an open position and a closed position of the mould. The shells and the sectors define an inner space that is intended to be brought into contact with the unvulcanized green form of the tire. In order to form the tread patterns, blades are attached to the sectors of the mould and protude into this inner space. For further details on a mould comprising such blades, reference could for example be made to documents EP-B1-1 758 743 and US-A1-2002/0139164.
The advantage of manufacturing by selective melting of superposed layers of powder, more commonly referred to as sintering, mainly lies in the fact that the shape of these blades may be modelled by a computer and that the blades may then be manufactured on the basis of this modelling by computer control of the beam of energy. In addition, this technique is highly suitable for the manufacture of elements of small sizes and of complex shapes, such as mould lining blades, which are difficult to manufacture with other processes.
When the selective melting is carried out by a laser beam, it is referred to as laser sintering. The laser sintering technique consists in manufacturing the blade layer after layer, by stacking the layers of powder, which are consolidated and fused on top of one another by the laser beam, in a stacking direction. The term “powder” is understood to mean a powder or a mixture of powders. The powder may for example be metallic or mineral, for example ceramic.
Conventionally, in order to ensure the preparation of the bed of powder prior to the sintering or melting operation, a layering device is used. Such a device mainly comprises means for storing the powder and distribution means capable of distributing the powder as a layer on a manufacturing plate. For further details on such layering devices, reference could for example be made to patent application WO-A2-2013/178825.
The first layer is deposited then welded directly to the manufacturing plate. The other layers are then formed successively so as to obtain a stack starting from the first layer.
Generally, the manufacture of a small-sized element, such as a lining blade, is carried out horizontally on the manufacturing plate so that its length is substantially parallel to the manufacturing plate. It is then referred to as horizontal-type manufacturing. This makes it possible to avoid having too high a blade height and to thus reduce the manufacturing time.
However, with such a type of manufacture, problems of non-compliance of the dimensional and geometric features may be faced. Indeed, the blades may have undulations or else bulky portions that create zones referred to as undercut zones, i.e. zones where a blade wall overhangs above a non-solidified powder zone. Such bulky portions are for example provided on the blades described in patent applications FR-A1-2 961 741 and WO-A1-2010/030276. Observed in these undercut zones of the blades are deformations, stress concentration phenomena that may generate cracks and a particularly high roughness. Furthermore, certain blade geometries cannot be manufactured because of such undercut zones.